Interpretive Summary: This work presents a method for the quantitation of nonylphenol ethoxylates (NPEOs) and octylphenol ethoxylates (OPEOs) in water, sediment, and suspended particulate matter, and three of their oxygenated deriviatives (carboxylates) in water. The alkylphenol ethoxylates (APEOs) were analyzed using isotopically labeled analogues that allowed direct correction for interferences and corrections for recovery, whereas the carboxylated derivatives were determined by external standard methods followed by confirmation using standard additions. The method was used to study APEO’s behavior in a wastewater treatment plant (WWTP), where total dissolved NP-ethoxylate concentrations were reduced by approximately 99% from influent (390 µg/L) to final effluent (4 µg/L), and total OP0-5EO concentration decreased 94% from 3.1 to 0.2 µg/L. In contrast, the carboxylated derivatives were formed during the process with NP0-1EC concentrations increasing from 1.4 to 24 'g/L. Short-chain APEOs were present in higher proportions in particulate matter, presumably due to greater affinity for solids compared to the long-chain homologues. NP (0.49 µg/L) and NP0-1EC (4.8 µg/L) were the only APEO-related compounds detected in a surface water sample from a WWTP-impacted estuary; implying that 90% of the mass was in the form of carboxylated derivatives. Sediment analysis showed nonylphenol to be the single most abundant compound in sediments from the Baltimore Harbor area, while differences in homologue distribution suggested the presence of treated effluent at some of the sites and non-treated sources in the rest.

Technical Abstract:
This work presents an LC-MS-MS-based method for the quantitation of nonylphenol ethoxylates (NPEOs) and octylphenol ethoxylates (OPEOs) in water, sediment, and suspended particulate matter, and three of their carboxylated derivatives in water. The alkylphenol ethoxylates (APEOs) were analyzed using isotope dilution mass spectrometry with [13C6]-labeled analogues, whereas the carboxylated derivatives were determined by external standard quantitation followed by confirmation using standard additions. The method was used to study APEO’s behavior in a wastewater treatment plant (WWTP), where total dissolved NP0-16EO concentration was reduced by approximately 99% from influent (390 µg/L) to final effluent (4 µg/L), and total OP0-5EO concentration decreased 94% from 3.1 to 0.2 µg/L. In contrast, the carboxylated derivatives were formed during the process with NP0-1EC concentrations increasing from 1.4 to 24 'g/L. Short-chain APEOs were present in higher proportions in particulate matter, presumably due to greater affinity for solids compared to the long-chain homologues. NP (0.49 µg/L) and NP0-1EC (4.8 µg/L) were the only APEO-related compounds detected in a surface water sample from a WWTP-impacted estuary; implying that 90% of the mass was in the form of carboxylated derivatives. Sediment analysis showed nonylphenol to be the single most abundant compound in sediments from the Baltimore Harbor area, while differences in homologue distribution suggested the presence of treated effluent at some of the sites and non-treated sources in the rest.